I've been on a site with bright purple around (3) MV terms in a section of switchgear. I've always heard about corona, and seen evidence as a white powdery substance, but never seen anything like this. My initial advice to the customer would be to re-terminate the conductors and perform a VLF test on the cables. There's enough of a loop under the lugs to do so. Can anyone provide some insight about how far down the cable beyond the termination) the insulation could be compromised, if at all? My understanding is that corona usually happens in the air gaps between the conductor and the insulation, or between conductors. Because we're talking about a cable and not a bus bar, it would seem like the terms weren't installed properly, and this corona has developed internally inside the cable. Other sections of the gear have the same phase-to-phase gaps with no issues. I don't know how old the terminations are, but they look like cold shrink, unlike some of the other terms in the gear which were wrapped. Any input is greatly appreciated.
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